<!DOCTYPE html>
<html lang="en">

<head>
  <meta charset="UTF-8">
  <meta http-equiv="X-UA-Compatible" content="IE=edge">
  <meta name="viewport" content="width=device-width, initial-scale=1.0">
  <title>Document</title>
  <style>
    button {
      font-size: 24px;
      border-radius: 4px;
      border: 2px solid transparent;
    }

    #red {
      background-color: red;
    }

    #blue {
      background-color: blue;
    }
  </style>
</head>

<body>
  <button id="red">Red Button</button>
  <button id="blue">Blue Button</button>
  <script src="./index.js" type="module"></script>
</body>

</html>